--- a/libtomcrypt/src/modes/ctr/ctr_start.c	Sat Jun 24 11:53:32 2017 +0800
+++ b/libtomcrypt/src/modes/ctr/ctr_start.c	Sat Jun 24 17:50:50 2017 +0800
@@ -6,7 +6,7 @@
  * The library is free for all purposes without any express
  * guarantee it works.
  *
- * Tom St Denis, [email protected], http://libtomcrypt.com
+ * Tom St Denis, [email protected], http://libtom.org
  */
 #include "tomcrypt.h"
 
@@ -46,6 +46,16 @@
       return err;
    }
 
+   /* ctrlen == counter width */
+   ctr->ctrlen   = (ctr_mode & 255) ? (ctr_mode & 255) : cipher_descriptor[cipher].block_length;
+   if (ctr->ctrlen > cipher_descriptor[cipher].block_length) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   if ((ctr_mode & 0x1000) == CTR_COUNTER_BIG_ENDIAN) {
+      ctr->ctrlen = cipher_descriptor[cipher].block_length - ctr->ctrlen;
+   }
+
    /* setup cipher */
    if ((err = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &ctr->key)) != CRYPT_OK) {
       return err;
@@ -55,7 +65,7 @@
    ctr->blocklen = cipher_descriptor[cipher].block_length;
    ctr->cipher   = cipher;
    ctr->padlen   = 0;
-   ctr->mode     = ctr_mode & 1;
+   ctr->mode     = ctr_mode & 0x1000;
    for (x = 0; x < ctr->blocklen; x++) {
        ctr->ctr[x] = IV[x];
    }
@@ -64,7 +74,7 @@
       /* increment the IV as per RFC 3686 */
       if (ctr->mode == CTR_COUNTER_LITTLE_ENDIAN) {
          /* little-endian */
-         for (x = 0; x < ctr->blocklen; x++) {
+         for (x = 0; x < ctr->ctrlen; x++) {
              ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
              if (ctr->ctr[x] != (unsigned char)0) {
                 break;
@@ -72,7 +82,7 @@
          }
       } else {
          /* big-endian */
-         for (x = ctr->blocklen-1; x >= 0; x--) {
+         for (x = ctr->blocklen-1; x >= ctr->ctrlen; x--) {
              ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
              if (ctr->ctr[x] != (unsigned char)0) {
                 break;
@@ -86,6 +96,6 @@
 
 #endif
 
-/* $Source: /cvs/libtom/libtomcrypt/src/modes/ctr/ctr_start.c,v $ */
-/* $Revision: 1.11 $ */
-/* $Date: 2006/11/05 01:46:35 $ */
+/* $Source$ */
+/* $Revision$ */
+/* $Date$ */